Glass electrophoresis microchip and method of manufacturing the same by mems fabrication

ABSTRACT

Embodiments of the present invention may provide a microchip applicable to an electrophoresis employing UV detection and a method of manufacturing the same. The microchip of the present invention has a glass channel plate, which is formed on an upper surface thereof with a loading channel and a separation channel and is provided on the upper surface thereof with an optical slit layer made of silicon except the channel region, and a glass reservoir plate, which is formed with sample solution reservoirs and buffer solution reservoirs. The loading channel and the separation channel are formed on the channel plate by deep reactive ion etching. The sample solution reservoirs and the buffer solution reservoirs are formed in the reservoir plate by sand blasting. The channel plate and the reservoir plate are combined by anodic bonding the optical slit layer and the reservoir plate. Electrodes for sample and electrodes for buffer are deposited by sputtering Pt with a shadow mask after anodic bonding.

BACKGROUND

1. Field

The present invention generally relates to a microchip forelectrophoresis, and more particularly to a glass microchip, which hasan optical slit made from silicon by MEMS fabrication to effectively cutoff a stray light. Further, the present invention relates to a method ofmanufacturing the same.

2. Background

A micro total analysis system (μTAS), which was established along withadvancements of nano and bio technologies, became an essentialfoundation for a bioMEMS technology. An electrophoretic analysis ismainly used in the μTAS. With regard to selecting channels in which asample is separated, the electrophoretic analysis is recently beingchanged from one way of using a fused silica capillary to another way ofusing a lab-on-a-chip, which is manufactured by MEMS fabrication andmicromachining technology. Such electrophoretic analysis using amicrochip is attracting great attention as an emergent analysistechnology. This is due to the treatment of a small amount of samples, afaster analysis, more convenient operation, a high throughput withimproved accuracy, etc.

Various samples such as proteins, DNAs, amino acids, cell particles,etc. can be analyzed by using the electrophoresis microchip. Theelectrophoresis microchip basically utilizes a microfluidics principle.The electrophoresis microchip is provided with a sample loading channel(into and out of which sample solution to be analyzed flows) and aseparation channel (into and out of which buffer solution flows), andwhich is crossed to the sample loading channel. Inlet and outletreservoirs of the sample solution and the buffer solution are providedwith electrodes so that electric fields can be applied to the sampleloading channel and the separation channel. While the sample solutionflows from the inlet reservoir to the outlet reservoir, a certain amountof sample solution is positioned at an intersection of the sampleloading channel and the separation channel by the electric field appliedto the sample loading channel. Then, particles dispersed in the samplesolution are separated according to the mobility differences by theelectric field applied to the separation channel. The dimensions of thechannel of the microchip are several tens μm to about 100 μm in widthand depth.

Plastics such as polydimethylsiloxane (PDMS), quartz, glass, silicon,etc. are used as a material for the microchip. The microchip made fromPDMS is used as a disposable chip and the manufacturing costs are low.On the contrary, the microchips made from quartz, glass, silicon, etc.are possible to be used repeatedly since they are manufactured by dryand wet etching and bonding, which require high process costs.

In case the microchip is made from quartz or glass, a UV detector can beintroduced in order to analyze the samples. FIG. 1 depicts anelectrophoresis system equipped with the UV detector introduced thereto.The UV detector has relatively low costs and can be convenientlyoperated compared to any other detector such as a fluorescence detector.In addition, since signals are received from the entire channel regionby means of zone detection, transports of the samples to be analyzed inthe channel can be observed in real time. In such an electrophoresissystem with the UV detector, in order to enhance a peak intensity (i.e.,a signal-to-noise ratio (S/N ratio) of UV light), a technology formanufacturing a microchip, which allows the incident UV light to focuson only the channel and the stray light to cut off except the channelregion, is necessary.

As a current technical state relevant to such a technology, thefollowing papers disclose microchips, wherein an optical slit made ofSi/SiO₂ is provided between the channel plate and the reservoir plate: apaper entitled “Single-step quantitation of DNA in microchipelectrophoresis with linear imaging UV detection and fluorescencedetection through comigration with a digest” (F. Xu et al.) published inthe Journal of Chromatography A, vol. 1051, pp. 147-153, 2004; a paperentitled “High-speed electrophoretic analysis of1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides on aquartz microchip with whole-channel UV detection” (S. Suzuki et al.)published in the Electrophoresis, vol. 24, pp. 3828-3833, 2003; a paperentitled “Fabrication of quartz microchip with optical slit anddevelopment of a linear imaging UV detector for microchipelectrophoresis systems” (H. Nakanishi et al.) published in theElectrophoresis, vol. 22, pp. 230-234, 2001; a paper entitled “Studieson SiO₂—SiO₂ bonding with hydrofluoric acid. Room temperature and lowstress bonding technique for MEMS” (H. Nakanishi et al.) published inthe Sensors and Actuators, vol. 79, pp. 237-244, 2000. Those microchipshave been developed to be limited to only quartz material and are beingmarketed by Shimadzu Instruments (Kyoto, Japan).

However, quartz material is expensive. In addition, both dry etching andwet etching are required in order to form the channels on the channelplate made from quartz. Therefore, there is a problem with the microchipmade from quartz in that its material is expensive and its process andmanufacturing costs are high. Because wet etching is apt to render thecross-sectional shape of the channel isotropic while causing undercutsin the channel, the channel of the microchip formed by wet etching isfurther or less etched than the desired depth and width. There isanother problem with the microchip made from quartz in that it isdifficult to bond the channel plate and the reservoir plate duringmanufacturing the microchip.

Accordingly, there is a need to provide an electrophoresis microchipmade from a more inexpensive material than quartz (e.g., glass) toreduce operation costs and to facilitate microchip supply. Further,there is a need to provide an electrophoresis microchip, wherein itschannels are formed by dry etching instead of wet etching in order torender the cross-sectional shape of the channel anisotropic and toreduce process costs. Furthermore, there is a need to provide anelectrophoresis microchip, which is configured such that a channel plateand a reservoir plate are easily bonded.

BRIEF DESCRIPTION OF THE DRAWINGS

Arrangements and embodiments may be described in detail with referenceto the following drawings in which like reference numerals refer to likeelements and wherein:

FIG. 1 depicts an electrophoresis system;

FIG. 2 is a photograph showing an electrophoresis microchip according tothe present invention;

FIG. 3 shows design diagrams of masks required to manufacture themicrochip according to the present invention;

FIG. 4 shows a manufacturing process of a channel plate;

FIG. 5 shows a manufacturing process of a reservoir plate;

FIG. 6 shows a bonding process of the channel plate and the reservoirplate;

FIG. 7 is a photograph showing a bonded wafer of the channel plate andthe reservoir plate, which is bonded to each other by anodic bonding;

FIG. 8 shows an electrode deposition process;

FIG. 9 is a photograph showing a shadow mask for electrode deposition;

FIG. 10 is a photograph showing the bonded wafer with the electrodesdeposited thereon;

FIG. 11 is a photograph taken with a scanning electron microscope, whichshows a cross-section of a channel taken along the line A-A′ of FIG. 2;

FIG. 12( a) shows an electropherogram and a gel image of electroosmoticflow velocity of a benzyl alcohol marker, which is measured by themicrochip of the present invention; and

FIG. 12( b) shows an electropherogram and a gel image of electoosmoticflow velocity of a benzyl alcohol marker, which is measured by any othermicrochip without an optical slit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

A detailed description may be provided with reference to theaccompanying drawings. One of ordinary skill in the art may realize thatthe following description is illustrative only and is not in any waylimiting. Other embodiments of the present invention may readily suggestthemselves to such skilled persons having the benefit of thisdisclosure.

FIG. 2 is a photograph showing an embodiment of a microchip constructedaccording to the present invention. The microchip 100 of this embodimentis sized to be 3.5 cm long and 1.25 cm wide.

The microchip 100 comprises a channel plate 110, a reservoir plate 120,electrodes for sample 131 and 132 and electrodes for buffer 133 and 134.The channel plate 110 is formed with a loading channel 111 (into and outof which a sample solution flows) and a separation channel 112 (into andout of which a buffer solution flows). The reservoir plate 120 is bondedto an upper side of the channel plate 110. The reservoir plate 120 has asample inlet reservoir 121 and a sample outlet reservoir 122, which arein communication with both ends of the loading channel 111. Thereservoir plate 120 also has a buffer inlet reservoir 123 and a bufferoutlet reservoir 124, which are in communication with both ends of theseparation channel 112, as well as align mark holes 125. The sampleinlet reservoir 121 and outlet reservoir 122, the buffer inlet reservoir123 and outlet reservoir 124, and the align mark holes 125 are formed atthe reservoir plate 120. The electrodes for sample 131 and 132 areformed to extend from an upper surface of the reservoir plate 120 to theinlet reservoir 121 and the outlet reservoir 122, respectively. Theelectrodes for buffer 133 and 134 are formed to extend from an uppersurface of the reservoir plate 120 to the inlet reservoir 123 and theoutlet reservoir 124, respectively. Between an upper surface of thechannel plate 110 and a lower surface of the reservoir plate 120, thereis provided an optical slit layer, which is composed of silicon, exceptthe region of the channels 111 and 121. Said optical slit layer isaccordingly formed on the channel plate 110.

The channel plate 110 is fabricated from a Silicon On Glass wafer (SOGwafer). The channels 111 and 112 are formed by dry etching (e.g., deepreactive ion etching) on a surface of the SOG wafer in accordance withpatterns of the channels. The reservoir plate 120 is fabricated from aglass wafer by drilling (e.g., sand blasting) the glass wafer inaccordance with patterns of the inlet reservoirs 121 and 123, the outletreservoirs 122 and 124, and the align mark holes 125. An upper surfaceof said optical slit layer, which is provided between the channel plate110 and the reservoir plate 120, and the lower surface of the reservoirplate 120 are anodic bonded to each other. The electrodes 131, 132, 133and 134 are formed by sputtering Pt.

The sample solution flows into the loading channel 111 from the inletreservoir 121 and passes through the loading channel 111 and then flowsout from the outlet reservoir 122. The buffer solution flows into theseparation channel 112 from the inlet reservoir 123 and passes throughseparation channel 112 and then flows out from the outlet reservoir 124.While the sample solution flows from the inlet reservoir 121 to theoutlet reservoir 122, a certain amount of sample solution is positionedat an intersection 113 of the channels 111 and 112 by an electric fieldapplied by the electrodes 131 and 132. Particles in the sample solutionlocated at the intersection 113 are moved into the separation channel112 according to their own mobility by an electric field applied by theelectrodes 133 and 134 to be thereby separated from the sample solution.Based on such electrophoretic phenomenon, the particles in the samplesolution can be analyzed by irradiating UV light into the separationchannel 112 and detecting the same.

The microchip 100, which is shown in FIG. 2, can be obtained by cuttingbonded wafer, which is formed with a plurality of microchips, by usingthe Nd:YAG laser.

MEMS fabrication for manufacturing the glass microchip 100 forelectrophoresis of the present invention will now be described withreference to FIGS. 3 and 10.

FIG. 3 shows design diagrams of masks required to manufacture themicrochip of the present invention. FIG. 3( a) is a design diagram of amask for channel-patterning. The mask for channel-patterning comprises aplurality of units shown in FIG. 3( a). An individual microchip is sizedto be 3.5 cm long and 1.25 cm wide. Each unit is formed with slits 21and 22 of 110 μm width for pattering the loading channel 111 and theseparation channel 112. FIG. 3( b) is a design diagram of a mask forreservoir-patterning. The mask for reservoir-patterning comprises aplurality of units shown in FIG. 3( b). Each unit is formed with fourholes 41 of 2.23 mm diameter for patterning the sample inlet reservoirand outlet 121 and 122 and the buffer inlet reservoir and outlet 123 and124 and two holes 42 of 1.0 mm diameter for patterning the align markhole 125. Both the mask for channel-pattering and the mask forreservoir-patterning are prepared as a film mask so as to be applicableto photolithography. FIG. 3( c) is a design diagram of a mask forelectrode-deposit. The mask for electrode-depositing comprises aplurality of units shown in FIG. 3( c). Each unit is formed with holes51, 52, 53 and 54, which correspond to the shapes of the electrodes forsample 131 and 132 and the electrodes for buffer 133 and 134,respectively.

FIG. 4 shows a manufacturing process of a channel plate.

In order to manufacture the channel plate 110, as shown in FIG. 4( a), aSilicon On Glass (SOG) wafer 10 of 4 inch diameter is prepared. In thisembodiment, a SOG wafer having a silicon layer 12 of 50 μm thickness anda glass layer 11 of 500 μm thickness is selected as the SOG wafer 10.The prepared SOG wafer 10 is immersed in Piranha solution(H₂SO₄:H₂O=1:3) for about 10 minutes. Thereafter, the SOG wafer iscleaned in deionized water using N₂ bubbles.

As shown in FIG. 4( b), a photo resist (PR) layer 13 is formed on asurface of the silicon layer 12 of the cleaned SOG wafer 10. Preferably,in order to enhance the adhesiveness of the PR layer 13 on the siliconlayer 12, moisture on the surface of the SOG wafer 10 is removed andhexamethyldisilazane (HMDS) is applied thereon, rendering the surface ofthe silicon layer 12 hydrophilic. Since the silicon layer is alwayscovered with a thin native oxide of 20-50 Å, when it reacts togetherwith HMDS, a strong bonding is obtained therebetween. The PR layer 13 isformed with a thickness of 10 μm by spinning the SOG wafer 10 at 2000rpm. Thereafter, soft baking is carried out at 110° C. for 2.5 minutesby a hot plate.

Next, patterning for forming the loading channel 111 and the separationchannel 112 is carried out on the PR layer 13 of the SOG wafer 10. Saidpattering is carried out with a photolithography method.

More specifically, as shown in FIG. 4( c), the PR layer 13 is exposed toUV light with an intensity of 34 mW/cm² using the film mask 20 forchannel-patterning and a mask aligner. The part of the PR layer 13,which is exposed to the UV light passing through the slits 21 and 22 ofthe film mask 20, is modified by such exposure. Accordingly, the PRlayer 13 is formed with the same pattern as the slits formed in the filmmask 20. Next, as shown in FIG. 4( d), if developed by a developer(e.g., MIF 400K) and cleaned in deionized water, then the part, which ismodified and patterned, is separated from the PR layer 13 and a desiredchannel 13 a is thus formed in the PR layer 13. In such a case, theformed channel 13 a is sized to be of about 110 μm width and of about 10μm depth. When the channel development is ascertained with the aimedwidth and depth by using a microscope and a profilometer, the SOG wafer10 is hard baked at 130° for 3 minutes.

Next, as shown in FIG. 4( e), the silicon layer 12 is etched by deepreactive ion etching (DRIE). DRIE can etch by a thickness of thousands Åto several μm by destroying molecular bonds by means of continuouscollision and acceleration caused by electrical attraction of the ionscreated within a vacuum environment and radicals. In this embodiment,the DRIE process of the silicon layer 12 is carried out by supplyingSF₆/O₂ (etching gas) at 160/16 sccm and C₄F₈ (passivating gas) at 120sccm under a switching condition of 100 mTorr pressures and 10 minutes.Since the PR layer 13 is formed on the silicon layer 12, the siliconlayer 12 is etched by DRIE in accordance with the channel pattern 13 aformed in the PR layer 13.

The etched portion does not become completely anisotropic, becausephysical and chemical etching may simultaneously occur in RIE. Aspressure is lower and energy is higher, the mean free paths of thereacting molecules become gradually longer than the etched depth andactivated particles actively collide against a bottom surface. Thus, theanisotropy of the etched portion is enhanced. If DRIE of the siliconlayer 12 is ended, then the SOG wafer 10 is cleaned in deionized water.

Next, as shown in FIG. 4( f), the SOG wafer is immersed in acetonesolution for 3 minutes, thereby stripping the PR layer 13. In addition,as a preprocess for DRIE of the glass layer 11, an aluminum layer 14 isdeposited on a back surface of the SOG wafer 10. Depositing the aluminumlayer 14 is carried out by thickness of 1 nm under a condition of 10 kVand 30 mA by means of an E-beam evaporator.

Next, as shown in FIG. 4( g), DRIE for forming the loading channel 111or the separation channel 112 in the glass layer 11 is performed. DRIEof the glass layer 11 is carried out at 4-10 mTorr and 60° C. using C₄H₈and He gas. C₄H₈ etches the glass layer 11 by reaction with the glasslayer 11. He gas reduces the isotropy of the channel shape to be etched,establishing a vertical trench. In such a case, since the silicon layer12, which is located on the glass layer 11, is already etched inaccordance with the channel 13 a formed in the PR layer 13, the glasslayer 11 is formed with the loading channel 111 and the separationchannel 112 in accordance with the channel shapes formed in the filmmask 20. That is, the silicon layer 12 can play a role as an etch maskduring DRIE of the glass layer 11.

After completing DRIE of the glass layer 11, as shown in FIG. 4( h), theSOG wafer 10 is immersed in sulfuric acid solution for 10 minutes,thereby stripping the aluminum layer 14 deposited on the back surface ofthe SOG wafer 10.

Next, as shown in FIG. 4( i), flattening the surface of the siliconlayer 12 is carried out so that a surface roughness of the silicon layer12 is reduced for subsequent bonding process of the channel plate andthe reservoir plate. Flattening the surface is carried out by chemicalmechanical polishing (CMP). When flattening the surface is completed,the thickness of the silicon layer 12 of the SOG wafer 10 becomes 10 μm.

The SOG wafer 10, which is fabricated through the above-describedprocesses, becomes the channel plate 110, wherein both the loadingchannel 111 and the separation channel 112 are formed on its uppersurface and the optical slit layer 140 made from silicon is formedthereon except the region of the channels 111 and 112.

FIG. 5 shows a manufacturing process of a reservoir plate.

As shown in FIG. 5( a), in order to manufacture the reservoir plate 120,a glass wafer 30 having a diameter of 4 inches and a thickness of 1 mmis prepared. In this embodiment, a glass wafer based on borosilicate,which has minimal impurities, and both surfaces of which is wellpolished, is selected as the glass wafer 30 to eliminate anydisturbances that occur during electrophoresis detection.

Next, as shown in FIG. 5( b), a dry film resist (DFR) layer 31 isattached on an upper surface of the glass wafer 30.

Thereafter, as shown in FIG. 5( c), patterning the reservoir shapes iscarried out with a photolithography method. More specifically, thedesired reservoir pattern is formed in the DFR layer 31 by disposing afilm mask 40 for reservoir-patterning above the DFR layer 31 andexposing the wafer 30 to UV light and developing and cleaning the wafer30.

Next, as shown in FIG. 5( d), the glass wafer 30 is formed with holes bysand blasting the wafer 30. Since the DFR layer 31 is formed with thepatterns corresponding to the sample inlet reservoir and outletreservoir, the buffer inlet reservoir and outlet reservoir, and thealign mark hole, the glass wafer 30 is formed with the sample inletreservoir and outlet reservoir, the buffer inlet reservoir and outletreservoir, and the align mark hole in accordance with the patterns ofthe DFR layer 31.

Next, as shown in FIG. 5( e), the glass wafer 30 is immersed in acetonesolution, thereby stripping the DFR layer 31.

The glass wafer 30, which is fabricated by the above-describedprocesses, becomes the reservoir plate 120, wherein the sample inletreservoir 121 and outlet reservoir 122, the buffer inlet reservoir 123and outlet reservoir 124 are drilled therethrough.

FIG. 6 shows a bonding process of the channel plate and the reservoirplate.

After disposing the reservoir plate 120 above the channel plate 110 asshown in FIG. 6( a), the channel plate 110 and the reservoir plate 120are bonded to each other. The microchip 100 of the present invention isfabricated by anodic bonding both of the plates 110 and 120.

For anodic bonding, a wafer bonder is utilized and a hot plate is heatedto 360° C. Further, the optical slit layer 140 made from silicon isconnected to an anode and the reservoir plate 120 is connected to acathode. A voltage of 800V is applied by a direct current power supplywhile a pressure of 3 kg_(f)/cm² is applied to both of the plates 110and 120 for 30 minutes. Then, (+) ions, which exist on the surface ofthe optical slit layer 140 made from silicon, are bonded to oxygen ions(−) of the reservoir plate 120 (i.e., the glass wafer 30), therebyaccomplishing anodic bonding.

Anodic bonding utilizes movements of Na ions and Li ions contained inglass. If a temperature is raised, then Na ions are moved to the cathodeand bonding is carried out. When Na ions are moved, space charge iscreated and potential drop occurs at an interface of the reservoir plate120 made from glass and the optical slit layer 140 made from silicon.High electrical field between the glass and silicon layer causes anelectrostatic force and covalent bond is made thereby. According to theinventor's experiment, a pin-hole phenomenon, which may occur inincomplete bonding, does not occur between the anodic bonded plates 110and 120. FIG. 7 is a photograph showing a bonded wafer of the channelplate and the reservoir plate by anodic bonding.

FIG. 8 shows an electrode deposition process. FIG. 9 is a photographshowing a shadow mask for electrode deposition.

The electrodes for sample 131 and 132 and the electrodes for buffer 133and 134 are formed as shown in FIG. 8. The electrodes 131, 132, 133 and134 are formed as a thin layer comprised of Pt and Ti by sputtering.

A mask 50 shown in FIG. 9 is a shadow mask fabricated for the purpose ofdepositing the electrodes. A silicon wafer having a diameter of 4 inchesis prepared as a shadow mask 50. The shadow mask 50 for electrodedepositing is fabricated by drilling the holes, through which anelectrode material passes during sputtering, in the prepared siliconwafer by means of the Nd:YAG laser.

As shown in FIG. 8, the electrodes are deposited by sputtering in astate where the shadow mask 50 is disposed above the bonded plates 110and 120.

Direct current sputtering is used in this embodiment. Since an amount ofelectric current is nearly proportional to a thickness of the thin layerin direct current sputtering, the deposited thin layer is highly uniformand the intensity of sputtering is high.

In the sputtering process of the present invention, a target material(Pt/Ti) is set as cathode, the bonded plates are set as anode, and Argas is used for creating ions. The shadow mask 50 is disposed above thebonded wafer and an internal pressure of a sputtering chamber is set to7 mTorr and Ar gas is injected thereinto. Further, a direct currentpower source of 100 W is applied. Then the injected Ar gas is ionized.Specifically, Ar emits energy while emitting an electron and the Ar⁺ions in the plasma environment are accelerated by electric potentialdifference with collision against a surface of a target material,thereby forming the thin layer. In order to enhance the effectiveness ofsputtering Pt, Ti is first sputtered by a thickness of 20 nm at a roomtemperature and then Pt is sputtered by a thickness of 500 nm.

The bonded wafer with the electrodes deposited thereon is fabricated bythe above-described processes, as shown in FIG. 10. The bonded wafer isprepared with a plurality of microchips (in this embodiment, tenmicrochips). The microchip 100 shown in FIG. 2 is fabricated by cuttingthe completed bonded wafer by means of the Nd:YAG laser. The completedmicrochip 100 is formed with the sample inlet reservoir 121 and thesample outlet reservoir 122 and the buffer inlet reservoir 123 and thebuffer outlet reservoir 124. Further, the completed microchip 100 isformed with the loading channel 111, the separation channel 112, and theoptical slit layer 140 made of silicon locating between the channelplate 110 and the reservoir plate 120 except the region of the channels111 and 112.

FIG. 11 is a photograph of a cross-section of the microchip taken alongthe A-A line of FIG. 2, which was actually manufactured by theabove-described processes. It was taken with a field emission scanningelectron microscope (Hitachi: S-4700). The characteristics of thechannel provided in the microchip become a factor having an importanteffect on the performance of the electrophoresis, by which a smallamount of samples must be analyzed. As can be seen from FIG. 11, thechannel 112 of the finished microchip 100 has a rectangularcross-section. That is, an anisotropic cross-section was obtained. Themeasured channel is 107 μm wide at its top and is 45 μm deep. It isestimated that a bottom surface of the channel is not even since anincomplete etching occurred due to the impurities contained in glass.Further, it can be clearly seen that the optical slit layer 140 madefrom silicon was formed between the channel plate 110 and the reservoirplate 120 by a thickness of 10 μm from FIG. 11. As such, since thechannel 112 is etched in an anisotropic cross-section by DRIE, thechannel can be precisely etched by desired depth and width. Furthermore,since etching can be carried out continuously in one direction (morespecifically, continuous etching in a depth direction of the channel) bydry etching such as DRIE, a so-called high-aspect-ratio channel can beformed. Due to the optical slit layer, the UV light irradiated to thechannel can be detected in the state where it focuses on only thechannel and the stray light cuts off except the channel region. Further,the UV light having passed through the channel does not undergo arefraction phenomenon, thereby enhancing detection efficiency.

The present inventor conducted an experiment, wherein it can beascertained that the glass microchip obtained by the above-describedfabricating process has the performance suitable for theelectrophoresis. The experiment was conducted by measuring anelectroosmotic flow velocity of a neutral marker. The experiment wasalso conducted on a glass microchip with an optical slit layer such asthe microchip of the present invention and other glass microchip withoutan optical slit layer. Microchip electrophoresis equipment used formeasurement was “MCE2010” (Shimadzu Corp., Japan). 50 mM Tris of pH10.7was used as buffer solution. Benzyl alcohol was used as the neutralmarker. An electric field of 500V and 5-10 μA was applied. According tothe experiment, the electroosmotic flow velocity was measured as 0.36mm/s. FIG. 12( a) shows an electrophoresis peak (i.e., electropherogram)and a gel image of the electoosmotic flow velocity of the benzyl alcoholmarker, which is measured using the microchip of the present invention.FIG. 12( b) shows an electrophoresis peak and a gel image of theelectoosmotic flow velocity of the benzyl alcohol marker, which ismeasured using any other microchip without an optical slit layer. Asshown in the electropherograms of FIGS. 12( a) and 12(b), the S/N ratioand the UV absorbance of the case with the optical slit layer made fromsilicon (e.g., FIG. 12( a)) was superior to those of the case withoutthe optical slit layer (e.g., FIG. 12( b)). The peak properties of theglass microchips are comparatively shown in below Table 1 according towhether the microchip has or does not have the optical slit layer madefrom silicon. As can be seen from Table 1, in the case with the opticalslit layer, the S/N ratio is enhanced about 3 times and the maximum UVabsorbance is enhanced about 1.7 times. Meanwhile, as measured using aquartz microchip with an optical slit layer made from Si/SiO₂ (itschannels are 110 μm wide and 50 μm deep), which can be available fromShimadzu Instruments (Japan), its electoosmotic flow velocity was 0.5mm/s and its maximum UV absorbance was 295±5 mAbs. The quartz microchipwas superior to the glass microchip in view of the electoosmotic flowvelocity and the maximum UV absorbance. However, the S/N ratio was shownto be nearly similar in both cases.

TABLE 1 Peak Properties Without optical slit With optical slit S/N Ratio5.5-6.6 14-23 Max. UV Absorbance(mAbs) 118 ± 5 195 ± 5

Embodiments of the present invention may provide a glass electrophoresismicrochip with an optical slit layer, which is applicable to anelectrophoresis employing UV detection. Further, embodiments of thepresent invention may provide a method of manufacturing such a microchipby MEMS fabrication. Since the microchip is made from glass,manufacturing costs are reduced compared to the prior art quartzmicrochip. Further, since the channels are formed by only the DRIEprocess instead of a wet etching process, the manufacturing time for themicrochip can be shortened and the process costs can also be reduced.Furthermore, since the cross-sectional shape of the channel becomesanisotropic by the dry etching of DRIE, the channel having a desiredsize can be precisely etched. The silicon layer interposed between thechannel plate and the reservoir plate serves as an optical slit layercapable of enhancing the S/N ratio and the absorbance of UV light. Inaddition, both the channel plate and the reservoir plate can be easilyanodic bonded due to the silicon layer. The microchip constructed inaccordance with the present invention can be utilized very usefully inelectrophoresis experimentation, wherein many microchips are frequentlyused due to a great quantity of samples to be analyzed. Moreover, itmotivates a μTAS study based on electrophoresis, thereby greatlyadvancing a bioMEMS technology.

A method of manufacturing an electrophoresis microchip may be provided.The method of the present invention may comprise the following steps:manufacturing a channel plate; manufacturing a reservoir plate;combining the channel plate and the reservoir plate; and formingelectrodes. Manufacturing a channel plate may comprise: patterning achannel shape on a silicon layer of a silicon on glass wafer; dryetching the silicon on glass wafer to form channels reaching a glasslayer through the silicon layer of the silicon on glass wafer; andflattening a surface of the silicon layer. Manufacturing a reservoirplate may comprise: patterning a reservoir shape on a surface of a glasswafer; and forming reservoirs by drilling through the glass wafer.Combining the channel plate and the reservoir plate may comprise anodicbonding the channel plate and the reservoir plate after disposing thereservoir plate on the silicon layer of the channel plate. Formingelectrodes may comprise forming electrodes extending from the reservoirplate to the reservoirs.

Patterning a channel shape during fabrication of the channel plate maycomprise: forming a photo resist layer on the silicon layer; disposing amask having the channel shape over the silicon on glass wafer andexposing the silicon on glass wafer to UV light; developing; andcleaning the silicon on glass wafer in deionized water. Manufacturing achannel plate may further comprise stripping the photo resist layerafter dry etching.

Dry etching of manufacturing a channel plate may comprise deep reactiveion etching (DRIE) the silicon layer and deep reactive ion etching(DRIE) the glass layer. Deep reactive ion etching the silicon layer mayutilize SF₆/O₆ as an etching gas and C₄F₈ as a passivating gas. Deepreactive ion etching the glass layer may utilize C₄H₈ as a reaction gasand He in order to obtain a vertical trench in the channel.

Pattering a reservoir shape during fabrication of the reservoir platemay comprise: applying a dry film resist layer on the glass wafer;disposing a mask having the reservoir shape drilled therethrough overthe glass wafer and exposing the glass wafer to UV light; developing;and cleaning the silicon on glass wafer in deionized water. Formingreservoirs may comprise sand blasting the glass wafer. Manufacturing areservoir plate may comprise stripping the dry film resist layer aftersand blasting.

Combining the channel plate and the reservoir plate may comprise anodicbonding, which is carried out in the state where the silicon layer isconnected to an anode and the reservoir plate is connected to a cathodeand a direct current power source is applied.

Forming electrodes may comprise sputtering a target material in acondition where both the channel plate and the reservoir plate combinedto each other are set as an anode and the target material constitutingthe electrodes is set as a cathode and a mask with a shape of theelectrodes drilled therethrough is disposed above the reservoir plate.

An electrophoresis microchip may also be provided. The microchip maycomprise the following: a channel plate formed on a upper surfacethereof with a loading channel and a separation channel crossed to theloading channel, the channel plate being composed of glass; an opticalslit layer disposed on the upper surface of the channel plate except thechannel region, the optical slit layer being composed of silicon; areservoir plate disposed on the optical slit layer and having a sampleinlet reservoir and a sample outlet reservoir and a buffer inletreservoir and a buffer outlet reservoir drilling therethrough, thesample inlet reservoir and outlet reservoir being in communication withone end and the other end of the loading channel respectively, thebuffer inlet reservoir and outlet reservoir being in communication withone end and the other end of the separation channel, the reservoir platebeing composed of glass; and electrodes for sample extending from theupper surface of the reservoir plate to the sample inlet reservoir andthe sample outlet reservoir respectively and electrodes for bufferextending from the upper surface of the reservoir plate to the bufferinlet reservoir and the buffer outlet reservoir respectively.

The channels may be formed by dry etching the channel plate. Thechannels may have a rectangular cross-section.

The optical slit layer may accordingly be formed on the channel plate.The optical slit layer and the reservoir plate may be bonded to eachother by anodic bonding.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. The appearances of such phrases in various places in thespecification are not necessarily all referring to the same embodiment.Further, when a particular feature, structure or characteristic isdescribed in connection with any embodiment, it is submitted that it iswithin the purview of one skilled in the art to effect such feature,structure or characteristic in connection with other ones of theembodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that variousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, numerous variations andmodifications are possible in the component parts and/or arrangements ofthe subject combination arrangement within the scope of the disclosure,the drawings and the appended claims. In addition to variations andmodifications in the component parts and/or arrangements, alternativeuses will also be apparent to those skilled in the art.

1. A method of manufacturing an electrophoresis microchip, comprising:(a) manufacturing a channel plate, comprising: patterning a channelshape on a silicon layer of a silicon on glass wafer; dry etching thesilicon on glass wafer to form channels reaching a glass layer throughthe silicon layer of the silicon on glass wafer; and flattening asurface of the silicon layer; (b) manufacturing a reservoir plate,comprising: patterning a reservoir shape on a surface of a glass wafer;and forming reservoirs by drilling through the glass wafer; (c)combining the channel plate and the reservoir plate after disposing thereservoir plate on the silicon layer of the channel plate; and (d)forming electrodes extending from the reservoir plate to the reservoirs.2. The method of claim 1, wherein patterning a channel shape comprises:forming a photo resist layer on the silicon layer; disposing a maskhaving the channel shape over the silicon on glass wafer and exposingthe silicon on glass wafer to UV light; developing; and cleaning thesilicon on glass wafer by deionized water, and wherein manufacturing achannel plate further comprises stripping the photo resist layer afterdry etching.
 3. The method of claim 1, wherein dry etching comprisesdeep reactive ion etching the silicon layer and deep reactive ionetching the glass layer.
 4. The method of claim 3, wherein deep reactiveion etching the silicon layer utilizes SF₆/O₆ as an etching gas and C₄F₈as a passivating gas.
 5. The method of claim 3, wherein deep reactiveion etching the glass layer utilizes C₄H₈ as a reaction gas and He inorder to obtain a vertical trench in the channel.
 6. The method of claim1, wherein pattering a reservoir shape comprises: applying a dry filmresist layer on the glass wafer; disposing a mask having the reservoirshape over the glass wafer and exposing the glass wafer to UV light;developing; and cleaning the silicon on glass wafer by deionized water.7. The method of claim 6, wherein forming reservoirs comprises sandblasting the glass wafer, and wherein manufacturing a reservoir platecomprises stripping the dry film resist layer after sand blasting. 8.The method of claim 1, wherein combining the channel plate and thereservoir plate comprises anodic bonding, which is carried out in thestate where the silicon layer is connected to an anode and the reservoirplate is connected to a cathode and a direct current power source isapplied.
 9. The method of claim 1, wherein forming electrodes comprisessputtering a target material in a condition where the channel plate andthe reservoir plate combined to each other are set as an anode and thetarget material constituting the electrodes is set as a cathode and amask with a shape of the electrodes drilled therethrough is disposedabove the reservoir plate.
 10. An electrophoresis microchip, comprising:a channel plate formed on an upper surface thereof with a loadingchannel and a separation channel crossed to the loading channel, thechannel plate being composed of glass; an optical slit layer disposed onthe upper surface of the channel plate except the channel region, theoptical slit layer being composed of silicon; a reservoir plate disposedon the optical slit layer and having a sample inlet reservoir and asample outlet reservoir and a buffer inlet reservoir and a buffer outletreservoir drilled therethrough, the sample inlet reservoir and outletreservoir being in communication with one end and the other end of theloading channel respectively, the buffer inlet reservoir and outletreservoir being in communication with one end and the other end of theseparation channel, the reservoir plate being composed of glass; andelectrodes for sample extending from the upper surface of the reservoirplate to the sample inlet reservoir and the sample outlet reservoirrespectively and electrodes for buffer extending from the upper surfaceof the reservoir plate to the buffer inlet reservoir and the bufferoutlet reservoir respectively.
 11. The microchip of claim 10, whereinthe channels are formed by dry etching the channel plate.
 12. Themicrochip of claim 11, wherein the channels have a rectangularcross-section.
 13. The microchip of claim 10, wherein the optical slitlayer is formed on the channel plate, and wherein the optical slit layerand the reservoir plate are bonded to each other by anodic bonding.